Lidia Sánchez

Lidia Sánchez
Universidad de León | UNILEON · Department of Mechanic Engineering, Computer and Aerospacial Sciences

PhD, Computer Science
Associate Professor, Universidad de León

About

93
Publications
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430
Citations

Publications

Publications (93)
Article
Full-text available
Livestock farming is assisted more and more by technological solutions, such as robots. One of the main problems for shepherds is the control and care of livestock in areas difficult to access where grazing animals are attacked by predators such as the Iberian wolf in the northwest of the Iberian Peninsula. In this paper, we propose a system to aut...
Chapter
The surface of machined parts is one of the most scrutinised criteria, since it determines their machinability. In this paper, texture descriptors obtained from the Grey Level Co-ocurrence Matrix (GCLM) are used to detect and classify six different types of surface defects of hot-rolled steel strip collected in the NEU dataset. Then, the texture fe...
Article
Full-text available
Machined workpieces must satisfy quality standards such as avoid the presence of burrs in edge finishing to reduce production costs and time. In this work we consider three types of burr that are determined by the distribution of the edge shape on a microscopic scale: knife-type (without imperfections), saw-type (presence of small splinters that co...
Chapter
Fulfilment of quality standards in manufacturing processes is an essential task and often increases production costs. Specifically, the appropriate edge finishing of machine workpieces is one of the requirements so as to avoid the presence of burrs. In this paper, a vision-based system that employs contour features is proposed to detect and classif...
Article
The eleven papers included in this special issue represent a selection of extended contributions presented at the 14th International Conference on Hybrid Artificial Intelligent Systems, HAIS 2019 held in León, Spain, September 4th-6th, 2019, and organized by University of León and BISITE research group. The International Conference on Hybrid Artifi...
Chapter
Manufacturing processes require to satisfy quality standards in the produced parts. In particular, the edge finishing must be burr-free, avoiding that it yields different problems such as wasting time removing them what increases the production cost and time. A burr can be noticed microscopically, but it can contain imperfections or evidence of poo...
Chapter
Quality standards involve objective procedures that guarantee the criteria keep constant during the process. In manufacturing, an important task that operators do by visual inspection is the evaluation of the surface finish of a machined workpiece. In this paper, a vision-based system that represents the image texture by a Local Binary Pattern vect...
Article
Micro milling is a versatile machining process owing to its capability to machine, by material removal, micro-sized components with complex geometrical features. However, micro milling tools wear quickly, being a key issue to determine tool wear condition in order to prevent excessive tool wear or a sudden tool breakage while machining, which would...
Article
Metallic pieces are typically machined by continuous tool passes, which usually causes regular patterns in the form of straight edges in the surface of the pieces. An irregular pattern on the surface of the piece implies a decrease of the quality of the machined piece. In this paper, we propose an acquisition system and a machine-vision based metho...
Article
Full-text available
Parallel Programming skills may require a long time to acquire. “Think in parallel” is a skill that requires time, effort, and experience. In this work, we propose to facilitate the students’ learning process in parallel programming by using instant messaging. Our aim was to find out whether students’ interaction through instant messaging tools is...
Article
This paper reports the experience of using the PAELLA algorithm as a helper tool in robust regression instead of as originally intended for outlier identification and removal. This novel usage of the algorithm takes advantage of the occurrence vector calculated by the algorithm in order to strengthen the effect of the more reliable samples and less...
Article
Full-text available
Version control systems’ usage is a highly demanded skill in information and communication technology professionals. Thus, their usage should be encouraged by educational institutions. This work demonstrates that it is possible to assess if a student can pass a computer science-related subject by monitoring its interaction with a version control sy...
Article
Full-text available
The emergence of autonomous vehicles with high needs for accuracy in location has hardened the requirements of the positioning systems used for navigation. Local Positioning Systems (LPS) have shown an excellent adaptation to these conditions, thanks to stability and reduction in the levels of positioning uncertainty. The accuracy achieved by metho...
Article
This paper reports the usage of the occurrence vector provided by the PAELLA algorithm in the context of robust regression. PAELLA was originally conceived as an outlier detection and data cleaning technique. A novel approach is to use this algorithm not for discarding outliers but to generate information related to the reliability of the observati...
Article
Expert systems provide valuable help for making decisions in those fields where the number of parameters involved is reasonably high. That is the case of plastic injection molding processes, where many parameters need to be determined in order to achieve parts with high quality. An intelligent system based on fuzzy logic is proposed and the members...
Conference Paper
Parallel Programming skills may require long time to acquire. "Think in parallel" is a skill which requires time, effort, and experience. In this work, we propose to facilitate the learning process in parallel programming by using instant messaging by students. Our aim is to find out if students' interaction through instant messaging is beneficial...
Conference Paper
Version Control Systems are commonly used by Information and communication technology professionals. They allow monitoring the single activity of different people working in the same project through all the project's lifetime. Thus, Version Control Systems are also used by educational institutions. The aim of this work is to demonstrate that the ac...
Article
Full-text available
Positioning asynchronous architectures based on time measurements are reaching growing importance in Local Positioning Systems (LPS). These architectures have special relevance in precision applications and indoor/outdoor navigation of automatic vehicles such as Automatic Ground Vehicles(AGVs) and Unmanned Aerial Vehicles (UAVs). The positioning er...
Article
Full-text available
Positioning asynchronous architectures based on time measurements are reaching growing importance in Local Positioning Systems (LPS). These architectures have special relevance in precision applications and indoor/outdoor navigation of automatic vehicles such as Automatic Ground Vehicles (AGVs) and Unmanned Aerial Vehicles (UAVs). The positioning...
Article
Full-text available
This work presents a new incremental-iterative method based on the boundary element method to solve 3D thermoelastic contact problems including a variable thermal contact resistance. The consideration of a variable thermal contact resistance implies that both thermal and thermoelastic problems are coupled since the variable thermal contact resistan...
Chapter
Milling workpiece present a regular pattern when they are correctly machined. However, if some problems occur, the pattern is not so homogeneous and, consequently, its quality is reduced. This paper proposes a method based on the use of texture descriptors in order to detect workpiece wear in milling automatically. Images are captured by using a bo...
Article
Full-text available
Time difference of arrival (TDOA) positioning methods have experienced growing importance over the last few years due to their multiple applications in local positioning systems (LPSs). While five sensors are needed to determine an unequivocal three-dimensional position, systems with four nodes present two different solutions that cannot be discard...
Chapter
Strength of materials and elasticity are included within the core subjects in the School of Engineering. Modeling and simulation are fundamental in early stages of engineering design and testing. For this reason, we propose the use of a Java application named BEMAPEC in combination with hand made problems to improve the motivation of the engineerin...
Article
This work presents a numerical methodology for modeling the Winkler supports and nonlinear conditions by proposing new boundary conditions. For the boundary conditions of Winkler support model, the surface tractions and the displacements normal to the surface of the solid are unknown, but their relationship is known by means of the ballast coeffici...
Book
This volume constitutes the refereed proceedings of the 14th International Conference on Hybrid Artificial Intelligent Systems, HAIS 2019, held in León, Spain, in September 2019. The 64 full papers published in this volume were carefully reviewed and selected from 134 submissions. They are organized in the following topical sections: data mining, k...
Article
Full-text available
In the current meso cutting technology industry, the demand for more advanced, accurate and cheaper devices capable of creating a wide range surfaces and geometries is rising. To fulfill this demand, an alternative single point cutting device with 6 degrees of freedom (6DOF) was developed. Its main advantage compared to milling has been the need fo...
Article
Ground-level ozone is a pollutant, greenhouse gas, and respiratory irritant which may facilitate skin cancer development and be involved in cardiovascular, respiratory and a range of other diseases. A re-distribution in the hourly ozone concentrations has occurred in the past decades while the interest in obtaining precise methods for the predictio...
Conference Paper
This paper reports the use of the PAELLA algorithm in the context of weighted regression. First, an experiment comparing this new approach versus probabilistic macro sampling is reported, as a natural extension of previous work. Then another different experiment is reported where this approach is tested against a state of the art regression techniq...
Conference Paper
This paper proposes an innovative single point cutting device that requires less maintenance than traditional micro-milling machines, being the cutting tools required simpler easier to develop. This satisfies the market demands on micro manufacturing, where devices must be more accurate and cheaper, able to create a diverse range of shapes and geom...
Conference Paper
Intelligent Systems are the best way to manage complex industrial processes with a high number of process parameters, like injection molding process. Specifically, Fuzzy Logic is a solution to estimate if the qualitative inspection of parts produced allows us to determine correct process parameter value setting to produce good quality parts. This p...
Conference Paper
Public health in developed countries is heavily affected by pollution specially in highly populated areas. Amongst the pollutants with greatest impact in health, ozone is particularly addressed in this paper due to importance of its effect on cardiovascular and respiratory problems and their prevalence on developed societies. Local authorities are...
Conference Paper
This paper proposes two parallel algorithms to optimise a Fortran application that solves thermoelastic contact problems between three-dimensional solids using the Boundary Element Method. Parallel libraries like MPI are of great use when trying to minimise the execution time of numerical codes. Experiments carried out show the effectiveness of par...
Conference Paper
This paper explores the benefit of using the PAELLA algorithm in an innovative way. The PAELLA algorithm was originally developed in the context of outlier detection and data cleaning. As a consequence, it is usually seen as a discriminant tool that categorizes observations into two groups: core observations and outliers. A new look at the informat...
Chapter
This paper presents a reliable machine vision system to automatically estimate and visualize tool wear in micro milling manufacturing. The estimation of tool wear is very important for tool monitoring systems and image sensors configure a cheap and reliable solution. This system provides information to decide whether a tool should be replaced so th...
Book
This volume of Advances in Intelligent and Soft Computing contains accepted papers presented at SOCO 2017, CISIS 2017 and ICEUTE 2017, all conferences held in the beautiful and historic city of León (Spain), in September 2017. Soft computing represents a collection or set of computational techniques in machine learning, computer science and some en...
Article
This article presents an Off-line handwritten digit recognition approach based on neural networks. We define a numeric character as a composition of vertical and horizontal strokes. After the preprocessing, we use dynamic zoning to retrieve the positions where vertical strokes - the main strokes - are joined to horizontal strokes. These features ar...
Conference Paper
In this paper, an experience to approach the competence about ethical aspects of the profession is presented. Following an existing methodology, several cases are presented to the students in order to determine if people involved have had a professional or ethical behaviour. Codes of professional ethics or conduct have been also discussed with the...
Conference Paper
This paper employs well-known techniques as Support Vector Machines and Neural Networks in order to classify images of boar sperm cells. Acrosome integrity gives information about if a sperm cell is able to fertilize an oocyte. If the acrosome is intact, the fertilization is possible. Otherwise, if a sperm cell has already reacted and has lost its...
Article
Improving students' involvement in universities classes is a challenging problem. This problem is particularly relevant in technical studies, even worst in computer related subjects where students tend to be very independent. In this paper, we propose the use of peer review as a methodology that can help students toget more involved and to develop...
Article
Full-text available
Un aspecto clave para cualquier institución educativa es formar a los individuos para que se desenvuelvan eficientemente en la sociedad. En la actualidad el contexto en que se desarrolla la formación es la era digital. En este contexto y en la coyuntura socioeconómica actual, se hace fundamental incrementar la futura empleabilidad de los discentes....
Conference Paper
Most workplace task and processes involve collaborative work between peers. This makes teamwork competence acquisition a key issue for educational institutions. This type of competence uses to be associated to project-based learning activities. In these activities students’ assessment is something complex and mostly based on the outcome developed b...
Article
We present a new approach for off-line intelligent word recognition based on a fuzzy classification model. First, we segment a word into its single characters, and label each pixel as vertical or as horizontal so that we can group all the pixels into vertical or horizontal strokes. Then, we use dynamic zoning to obtain the locations of the connecti...
Conference Paper
In this research a parallel version of two existing algorithms that implement Maximum Likelihood Scale Invariant Map (MLHL-SIM) and Scale Invariant Map (SIM) is proposed. By using OpenMP to distribute the independent iterations of for-loops among the available threads, a significant reduction in the computation time for all the experiments is achie...
Article
With the size digital collections are currently reaching, retrieving the best match of a document from large collections by comparing hundreds of tags is a task that involves considerable algorithm complexity, even more so if the number of tags in the collection is not fixed. For these cases, similarity search appears to be the best retrieval metho...
Conference Paper
One of the main aims of Higher Education institutions in the present socio-economic landscape is to train in a efficient way future workers. In order to do so these institutions invest lot of money and resources although this does not guarantee the improvement of students' employability. The problems they have to find a proper work is many times re...
Article
This paper introduces an expert system for handwritten digit recognition. The system considers that a numeric handwritten character can be decomposed into vertical and horizontal strokes. Then, the positions where horizontal strokes are connected to the vertical strokes are extracted as features using dynamic zoning. These features are laid into a...
Article
This article introduces a methodology for intelligent character recognition based on a new feature extraction technique that relies on the number of vertical strokes and the relative positions of the horizontal strokes connected to them. We also propose a new grammar in order to feed these features into a Deterministic Finite Automaton (DFA) that w...
Article
In this paper, we propose a new approach for off-line intelligent word recognition. Firstly, we segment a word into its single characters. Then, we tag every pixel of a character as vertical or horizontal and group them into vertical and horizontal strokes. We propose as main features the locations of the joints between a vertical stroke and each o...
Article
In this paper, we compare different methods to solve systems of linear equations in order to determine which one allows us to reduce as much as possible the execution time. We consider contact problems that are solved by applying the Boundary Element Method that involves the resolution of different systems of linear equations. Depending on the kind...
Article
The aim of this paper is to analyze the impact of developing projects in collaborative environments within the Bologna Process framework and the European Space for Higher Education context as a rewarding tool for the professional future of University students, attempting not only to provide them with the traditional technical competences, but also...
Article
This paper proposes a method for assessing the acrosome state of boar spermatozoa heads using digital image processing. We use gray level images in which spermatozoa have been labeled as acrosome-intact or acrosome damaged using the information of a coupled fluorescent image. The heads are segmented obtaining the outer head contour. A set of "n" in...
Conference Paper
This work proposes a new stroke based methodology for handwritten character recognition. After the pre-processing, several steps are involved to achieve the recognition. First, the character is segmented into its strokes. Then, we determine the maximum length of the longest horizontal segment that can be inscribed on a stroke. We also compute that...
Article
The turbine synchronization phenomenon is of great interest in order to estimate the flicker produced by a wind farm. This paper proposes an initial approach to analyze the appearance of this phenomenon by the use of various image processing techniques: a method to automatically calculate the angular frequency of an unknown number of wind turbines...
Conference Paper
Full-text available
This paper proposes a method to calculate the angular frequency of a wind turbine by using Artificial Vision techniques. For a given video in which several wind turbines appear, the set of frames that compose it are taken out. Then, a certain frame is analyzed to determine the wind turbines presented in the image. To deal with that, a preprocessing...
Conference Paper
In this work we review three methods proposed to estimate the fraction of alive sperm cells in boar semen samples. Images of semen samples are acquired, preprocessed and segmented in order to obtain images of single sperm heads. A model of intracellular density distribution characteristic of alive cells is computed by averaging a set of images of c...
Conference Paper
Full-text available
Insemination techniques in the veterinary field demand more objective methods to control the quality of sperm samples. In particular, different factors may damage a number of sperm cells that is difficult to predict in advance. This paper addresses the problem of quantifying the proportion of damaged/intact sperm cells in a given sample based on co...
Article
We consider images of boar spermatozoa obtained with an optical phase-contrast microscope. Our goal is to automatically classify single sperm cells as acrosome-intact (class 1) or acrosome-damaged (class 2). Such classification is important for the estimation of the fertilization potential of a sperm sample for artificial insemination. We segment t...
Article
Full-text available
Automatic assessment of boar sperm head images according to their acrosome status is a challenge task in the veterinary field. In this paper we explore how much information texture features can provide for this task. A neural network-based machine that employs texture descriptors derived from the discrete wavelet transform is proposed as a classifi...
Article
Full-text available
Due to the impact of the new technologies in our Society, special efforts to use them for teaching-learning computer architectures have been done. This work presents a simulator of a simple architecture (Simple-2) using two different technologies: Java and C#. In the one hand, the Java version is an applet which runs inside a web browser; in the ot...
Article
Full-text available
The impact of the Internet on Society also affects learning at University. Students use not only printed books and their own notes, but also the information available on the Net. WebQuests are learning tools that help the students use the In- ternet, but under the supervision of the lecturer, who has previously selected the most interesting sites t...
Article
This work presents a boar semen image classification by analyzing the sperm head texture. We have considered four techniques: Laws, coocurrence matrices, Legendre and Zernike moments. We have applied them to classify sperm head images as damage or not damage, comparing their efficiency. From the coocurrence matrices, 4 features are computed (contra...
Article
Full-text available
Automatic assessment of boar sperm head images according to their acrosome status is a challenge task in the veterinary field. In this paper we explore how much information texture features can provide for this task. A neural network-based machine that employs texture descriptors derived from the discrete wavelet transform is proposed as a classifi...